Victor Falls Earthcache
This earthcache is designed to introduce you to some of the unique geology of Victor Falls - this area is a relatively new Bonney Lake Park, with ample parking, picnic tables and a scenic overlook towards the Victor Falls. Please follow all posted signs and rules and most importantly DO NOT GO BEYOND THE FENCELINE. As a reminder, this is an Earthcache! As such there is no physical container to find, but rather this cache will ask you to make observations, apply the lesson below to answer several questions, and then email or message those answers to the CO in order to claim your smiley! Take your time, enjoy the view and collect your smiley!
Victor Falls - A Geologic History
Victor Falls is one of the few significant low land waterfalls to be found in the Puget Sound metropolitan area. The falls occur as Fennel Creek plunges over an escarpment carved into a thick deposit of sedimentary rock, plunging approximately 68 feet in a broad curtain of water. Both below and above the falls the creek flows more placidly through a valley thickly covered in brush and small tree growth. The existence of a waterfall of the size of Victor Falls at an elevation so close to sea level in the Puget Sound Basin can be attributed to the violent past of Mount Rainier.
The falls are formed where Fennel Creek runs across a resistant layer of mudflow deposit which was emplaced by the Osceola Mudflow
which occured about 5,600 years ago during an eruption of Mount Rainier which saw a portion of the northeast flank of the mountain collapse. The resulting lahar traveled all the way down the White River valley and emptied into the South Valley, and is thought to be responsible for redirecting the White River from emptying into Puget Sound via the Duwamish River to its current course of merging with the Puyallup River in Sumner. Lahar flows are comprised of pyroclastic rubble, mud, glacial debris and ash which combine into a slurry as it spreads out from a volcano. This flow can solidify over time creating a hard substrate. For more information about Lahars, consider heading into the Orting Valley to take a look at GCA99G4.
The exact size of the basin of Fennel Creek is difficult to determine, but the drainage appears to cover an area of at least 8 square miles. Given that none of this area is situated more than 700 feet above sea level however, the amount of water in the creek will be directly proportional to the amount of precipitation which the area has received in the immediate past weeks or months. During the winter the falls flow with ample vigor, however during the summer the volume of the creek will be reduced considerably, potentially being reduced to just a trickle in dry years.
Waterfall Geology
Waterfall formation is based around the basic principle that there is a watercourse (recognizing that water is an erosive agent) traversing over different layers of rock each with different rates of erosion. In other words, you have a river or stream flowing over hard rock (where erosion is slow) and also flowing over soft rock (where erosion is more rapid). Over time, the soft rock is further cut into by the water ultimately making the watercourse steeper beyond the hard rock layer.
This steepening effect also accelerates erosion as the influence of gravity on the water increases the water’s speed. With the watercourse continuing to cut into the softer rock, the waterfall gets taller, the plunge pool gets deeper, and the soft rock directly beneath the hard rock gets undercut. The undercutting will continue until the region runs out of the hard rock layer. At that point, the watercourse will revert over time to being a stream or rapid.
Questions
In order to log this cache as a find and earn your smiley you must answer the below questions. Please send your answers in a timely manner to the Cache Owner who can be contacted via the message center (link to profile at the top of this cache page). You may log your find immediately, no need to wait for your answers to be validated - I will contact you if there are any issues.
- Examine the waterfall. Does the erosive process seem to be creating an overhang, or is the waterfall relatively uniform in erosion down the cliff-face?
- Based on this observation, and knowing that this waterfall was created as a result of a lahar deposit - do you think that the lahar deposit is a harder or weaker stone compared to the bedrock in the area?
- Geologists note that this fall likely formed as a result of the Osceola Mudflow which occurred some 5,600 years ago. Given what you've learned about waterfall erosion, do you think this will be a long lived or a short lived waterfall in terms of geologic time? Why or why not?
- Take a photo of yourself in front of GZ and include it in your log or send it to me. If you prefer not to show your face, you may instead take a photo of a geocaching specific object, or a piece of paper with your caching handle written on it in front of the falls.
References:
- https://www.world-of-waterfalls.com/how-are-waterfalls-formed/
- https://www.waterfallsnorthwest.com/waterfall/Victor-Falls-3245
- https://www.usgs.gov/programs/VHP/lahars-move-rapidly-down-valleys-rivers-concrete